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Dr. S. M. Condren Chapter 8 Atomic Electron Configurations and Chemical Periodicity

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Dr. S. M. Condren ATOMIC ELECTRON CONFIGURATIONS AND PERIODICITY

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Dr. S. M. Condren Atomic Orbitals Types of orbitals found in the known elements: s, p, d, and f schools play defensive football Packer version: secondary pass defense fails

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Dr. S. M. Condren Atomic Orbitals Shapes s – spherical p – dumbbell d – complex f – very complex

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Dr. S. M. Condren Arrangement of Electrons in Atoms Electrons in atoms are arranged as SUBSHELLS (l) ORBITALS (m l ) SHELLS (n)

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Dr. S. M. Condren Each orbital can be assigned no more than 2 electrons! This is tied to the existence of a 4th quantum number, the electron spin quantum number, m s. Arrangement of Electrons in Atoms

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Dr. S. M. Condren Electron Spin Quantum Number, m s Can be proved experimentally that electron has a spin. Two spin directions are given by m s where m s = +1/2 and -1/2. Can be proved experimentally that electron has a spin. Two spin directions are given by m s where m s = +1/2 and -1/2.

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Dr. S. M. Condren Electron Spin and Magnetism Diamagnetic : NOT attracted to a magnetic fieldDiamagnetic : NOT attracted to a magnetic field Paramagnetic : substance is attracted to a magnetic field.Paramagnetic : substance is attracted to a magnetic field. Substances with unpaired electrons are paramagnetic.Substances with unpaired electrons are paramagnetic.

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Dr. S. M. Condren Measuring Paramagnetism Paramagnetic : substance is attracted to a magnetic field. Substance has unpaired electrons. Diamagnetic : NOT attracted to a magnetic field Active Figure 8.2

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Dr. S. M. Condren n ---> shell1, 2, 3, 4,... l ---> subshell0, 1, 2,... n - 1 m l ---> orbital -l l m s ---> electron spin+1/2 and -1/2 n ---> shell1, 2, 3, 4,... l ---> subshell0, 1, 2,... n - 1 m l ---> orbital -l l m s ---> electron spin+1/2 and -1/2 QUANTUM NUMBERS Now there are four!

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Dr. S. M. Condren Pauli Exclusion Principle No two electrons in the same atom can have the same set of 4 quantum numbers. That is, each electron has a unique address.

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Dr. S. M. Condren Electrons in Atoms When n = 1, then l = 0 this shell has a single orbital (1s) to which 2e- can be assigned this shell has a single orbital (1s) to which 2e- can be assigned When n = 2, then l = 0, 1 2s orbital 2e- 2s orbital 2e- three 2p orbitals6e- three 2p orbitals6e- TOTAL = 8e-

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Dr. S. M. Condren Electrons in Atoms When n = 3, then l = 0, 1, 2 3s orbital 2e- 3s orbital 2e- three 3p orbitals6e- three 3p orbitals6e- five 3d orbitals10e- TOTAL = 18e- When n = 3, then l = 0, 1, 2 3s orbital 2e- 3s orbital 2e- three 3p orbitals6e- three 3p orbitals6e- five 3d orbitals10e- TOTAL = 18e-

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Dr. S. M. Condren Electrons in Atoms When n = 4, then l = 0, 1, 2, 3 4s orbital 2e- 4s orbital 2e- three 4p orbitals6e- three 4p orbitals6e- five 4d orbitals10e- seven 4f orbitals14e- seven 4f orbitals14e- TOTAL = 32e- And many more!

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Dr. S. M. Condren

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Electrons generally assigned to orbitals of successively higher energy.Electrons generally assigned to orbitals of successively higher energy. For H atoms, E = - C(1/n 2 ). E depends only on n.For H atoms, E = - C(1/n 2 ). E depends only on n. For many-electron atoms, energy depends on both n and l.For many-electron atoms, energy depends on both n and l. Electrons generally assigned to orbitals of successively higher energy.Electrons generally assigned to orbitals of successively higher energy. For H atoms, E = - C(1/n 2 ). E depends only on n.For H atoms, E = - C(1/n 2 ). E depends only on n. For many-electron atoms, energy depends on both n and l.For many-electron atoms, energy depends on both n and l. Assigning Electrons to Atoms

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Dr. S. M. Condren Electron Filling Order

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Dr. S. M. Condren LED Traffic Lights Chapter 7, Problem 3, page 326 text

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Dr. S. M. Condren 1 1 s value of n value of l no. of electrons spdf notation for H, atomic number = 1 Two ways of writing configs. One is called the spdf notation. Writing Atomic Electron Configurations

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Dr. S. M. Condren One electron has n = 1, l = 0, m l = 0, m s = + 1/2 Other electron has n = 1, l = 0, m l = 0, m s = - 1/2 Writing Atomic Electron Configurations Other is called the orbital box notation

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Dr. S. M. Condren See Toolbox on CD for Electron Configuration tool.

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Dr. S. M. Condren Electron Configurations and the Periodic Table

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Dr. S. M. Condren Group 1A Atomic number = 3 1s 2 2s 1 ---> 3 total electrons Lithium

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Dr. S. M. Condren Group 2A Atomic number = 4 1s 2 2s 2 ---> 4 total electrons Beryllium

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Dr. S. M. Condren Group 3A Atomic number = 5 1s 2 2s 2 2p 1 ---> 5 total electrons 5 total electrons Boron

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Dr. S. M. Condren Group 4A Atomic number = 6 1s 2 2s 2 2p 2 ---> 6 total electrons 6 total electrons Here we see for the first time HUNDS RULE. When placing electrons in a set of orbitals having the same energy, we place them singly as long as possible. Carbon

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Dr. S. M. Condren Group 5A Atomic number = 7 1s 2 2s 2 2p 3 ---> 7 total electrons 7 total electrons Nitrogen

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Dr. S. M. Condren Group 6A Atomic number = 8 1s 2 2s 2 2p 4 ---> 8 total electrons 8 total electrons Oxygen

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Dr. S. M. Condren Group 7A Atomic number = 9 1s 2 2s 2 2p 5 ---> 9 total electrons 9 total electrons Fluorine

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Dr. S. M. Condren Group 8A Atomic number = 10 1s 2 2s 2 2p 6 ---> 10 total electrons 10 total electrons Note that we have reached the end of the 2nd period, and the 2nd shell is full! Neon

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Dr. S. M. Condren Group 1A Atomic number = 11 1s 2 2s 2 2p 6 3s 1 or neon core + 3s 1 neon core + 3s 1 [Ne] 3s 1 (uses rare gas notation) Note that we have begun a new period. All Group 1A elements have [core]ns 1 configurations. Sodium

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Dr. S. M. Condren Group 3A Atomic number = 13 1s 2 2s 2 2p 6 3s 2 3p 1 [Ne] 3s 2 3p 1 All Group 3A elements have [core] ns 2 np 1 configurations where n is the period number. Aluminum

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Dr. S. M. Condren All Group 5A elements have [core ] ns 2 np 3 configurations where n is the period number. Group 5A Atomic number = 15 1s 2 2s 2 2p 6 3s 2 3p 3 [Ne] 3s 2 3p 3 Yellow P Red P Phosphorus

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Dr. S. M. Condren Group 2A Atomic number = 20 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 [Ar] 4s 2 All Group 2A elements have [core]ns 2 configurations where n is the period number. Calcium

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Dr. S. M. Condren All 4th period elements have the configuration [argon] ns x (n - 1)d y and so are d-block elements. CopperIronChromium Transition Metals Table 8.4

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Dr. S. M. Condren Transition Element Configurations 3d orbitals used for Sc-Zn (Table 8.4)

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Dr. S. M. Condren

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Board Work V – electron configuration Cr – electron configuration Mn – electron configuration Ni – electron configuration Cu – electron configuration Zn – electron configuration

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Dr. S. M. Condren Magnetism Spins are aligned with an applied magnetic field. Paramagnetism Spins are randomized by thermal energy. Ferromagnetism Spins are aligned with or against an applied magnetic field. Spins are ordered in magnetic domains.

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Dr. S. M. Condren NMR and MRI 800 MHz, 18.8 T NMR spectrometerOpen Magnet Design MRI Nuclei also have spin and nuclear quantum numbers

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Dr. S. M. Condren Memory Metal

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Dr. S. M. Condren Nitinol, NiTi

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Dr. S. M. Condren Lanthanides and Actinides All these elements have the configuration [core] ns x (n - 1)d y (n - 2)f z and so are f-block elements. Cerium [Xe] 6s 2 5d 1 4f 1 Uranium [Rn] 7s 2 6d 1 5f 3

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Dr. S. M. Condren Lanthanide Element Configurations 4f orbitals used for Ce - Lu and 5f for Th - Lr (Table 8.2)

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Dr. S. M. Condren

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To form cations from elements remove 1 or more e- from subshell of highest n [or highest (n + l)]. P [Ne] 3s 2 3p 3 - 3e- ---> P 3+ [Ne] 3s 2 3p 0 Ion Configurations

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Dr. S. M. Condren Ion Configurations For transition metals, remove ns electrons and then (n - 1) electrons. Fe [Ar] 4s 2 3d 6 loses 2 electrons ---> Fe 2+ [Ar] 4s 0 3d 6 To form cations, always remove electrons of highest n value first!

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Dr. S. M. Condren Quantum Numbers What is one of the sets of quantum numbers for the 4s electrons in calcium? n = 4; l = 0; m l = 0; s = +1/2or n = 4; l = 0; m l = 0; s = -1/2

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Dr. S. M. Condren Quantum Numbers What is one of the sets of quantum numbers for the 3p electrons in sulfur? n = 3; l = 1; m l = +1; s = +1/2or n = 3; l = 1; m l = +1; s = -1/2or n = 3; l = 1; m l = 0; s = +1/2or n = 3; l = 1; m l = 0; s = -1/2or n = 3; l = 1; m l = -1; s = +1/2or n = 3; l = 1; m l = -1; s = -1/2

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Dr. S. M. Condren Quantum Numbers What is one of the sets of quantum numbers for the 3d electrons in Fe? n = 3; l = 2; m l = +2; s = +1/2 or n = 3; l = 2; ml = +2; s = -1/2 or n = 3; l = 2; ml = +1; s = +1/2or n = 3; l = 2; ml = +1; s = -1/2 or n = 3; l = 2; ml = 0; s = +1/2or n = 3; l = 2; ml = 0; s = -1/2 or n = 3; l = 2; ml = -1; s = +1/2 or n = 3; l = 2; ml = -1; s = -1/2 or n = 3; l = 2; ml = -2; s = +1/2or n = 3; l = 2; ml = -2; s = -1/2

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Dr. S. M. Condren Announcements You may bring a 4x6 index card with information A periodic table and a table of thermodynamic data will be furnished. You need to know your TAs name and your section number. Photo ID will be required when submitting your exam.

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Dr. S. M. Condren Announcements Teaching Assistant _________________________ Section _____ Name _________________________________ c General Chemistry 103 Hour Exam 2 Nov. 6, 2006 ALL WORK MUST APPEAR ON TEST FOR ANY CREDIT. Work includes stating the question in a mathematical form. A box should be drawn around the answer to be graded for a problem.

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Dr. S. M. Condren Announcements Last day to drop Suzie and Christie have papers to return, please see them after class

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Dr. S. M. Condren Bonus Points Exam II – worth 105 points, count as pts - Available through Other Lecture Documents this week, due Friday Nov. 10 Exam III – worth 105 points, count as pts - Available through Other Lecture Documents later, due Friday Dec. 15

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Dr. S. M. Condren How do we know the configurations of ions? Determine the magnetic properties of ions. Sample of Fe 2 O 3 Sample of Fe 2 O 3 with strong magnet Ion Configurations

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Dr. S. M. Condren General Periodic Trends Atomic and ionic sizeAtomic and ionic size Ionization energyIonization energy Electron affinityElectron affinity Higher effective nuclear charge Electrons held more tightly Larger orbitals. Electrons held less tightly.

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Dr. S. M. Condren Effective Nuclear Charge, Z* AtomZ* Experienced by Electrons in Valence Orbitals Li+1.28 Be B+2.58 C+3.22 N+3.85 O+4.49 F+5.13 Increase in Z* across a period [Values calculated using Slaters Rules]

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Dr. S. M. Condren Orbital Energies Orbital energies drop as Z* increases

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Dr. S. M. Condren Atomic Radii

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Dr. S. M. Condren Atomic Size Size goes UP on going down a group.Size goes UP on going down a group. Because electrons are added further from the nucleus, there is less attraction.Because electrons are added further from the nucleus, there is less attraction. Size goes DOWN on going across a period.Size goes DOWN on going across a period.

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Dr. S. M. Condren Size decreases across a period owing to increase in Z*. Each added electron feels a greater and greater + charge. Large Small Increase in Z* Atomic Radius

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Dr. S. M. Condren Trends in Atomic Size

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Dr. S. M. Condren Sizes of Transition Elements 3d subshell is inside the 4s subshell. 4s electrons feel a more or less constant Z*. Sizes stay about the same and chemistries are similar!

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Dr. S. M. Condren Density of Transition Metals 6th period 5th period 4th period

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Dr. S. M. Condren Ion Sizes Does the size go up or down when losing an electron to form a cation?

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Dr. S. M. Condren CATIONS are SMALLER than the atoms from which they come.CATIONS are SMALLER than the atoms from which they come. The electron/proton attraction has gone UP and so size DECREASES.The electron/proton attraction has gone UP and so size DECREASES. Li,152 pm 3e and 3p Li +, 78 pm 2e and 3 p + Ion Sizes Forming a cation.

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Dr. S. M. Condren Ion Sizes Does the size go up or down when gaining an electron to form an anion?

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Dr. S. M. Condren ANIONS are LARGER than the atoms from which they come.ANIONS are LARGER than the atoms from which they come. The electron/proton attraction has gone DOWN and so size INCREASES.The electron/proton attraction has gone DOWN and so size INCREASES. Trends in ion sizes are the same as atom sizes.Trends in ion sizes are the same as atom sizes. F, 71 pm 9e and 9p F -, 133 pm 10 e and 9 p - Ion Sizes Forming an anion.

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Dr. S. M. Condren Trends in Ion Sizes

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Dr. S. M. Condren Trends in Ionization Energy

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Dr. S. M. Condren Li Na K B AlAlAlAl 2nd IE / 1st IE

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Dr. S. M. Condren Electron Affinity A few elements GAIN electrons to form anions. Electron affinity is the energy involved when an atom gains an electron to form an anion. A(g) + e- ---> A - (g) A(g) + e- ---> A - (g) E.A. = E

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Dr. S. M. Condren Electron Affinity of Oxygen E is EXOthermic because O has an affinity for an e -. [He] O atom EA = kJ + electron O [He] - ion

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Dr. S. M. Condren Electron Affinity of Nitrogen E is zero for N - due to electron- electron repulsions. EA = 0 kJ [He] Natom [He] N - ion + electron

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Dr. S. M. Condren Announcements You may bring a 4x6 index card with information A periodic table and a table of thermodynamic data will be furnished. You need to know your TAs name and your section number. Photo ID will be required when submitting your exam.

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Dr. S. M. Condren Announcements Last day to drop Suzie and Christie have papers to return, please see them after class

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